Disc rubbing when out of the saddle

[Loukas]

I'm getting a very distracting disc rubbing noise from the front wheel every time I go out of the saddle, I have new carbon wheels and I fear those aren't rigid enough....
One thing I've noticed is that the Thru axle (12x100) is very light..., is it possible that a too light Thru axle impacts the overall wheel rigidigity?
Another thought, is it possible that the spokes have not enough tension? they look ok though
thanks!

[1415chris]

Since the rotors are mounted directly onto the hubs, that shound not have an impact.

[ms6073]

I would suspect your front rotor is ever so slightly out of true and if it is a flat mount caliper, then possibly the caliper is not square to the rotor face such that when you are out of the saddle, your fork blades flex a bit causing a momentary change in the caliper alignment.

[bobrayner]

If it was a rear wheel, the obvious culprit is that the wheel works loose and wobbles laterally - due to a loose axle or something like that - when there's a stronger torque from the chain. That can take the disc out of its usual alignment, and it can cause the tyre to rub on a chainstay.

With a front wheel, there's less that can go wrong. However, although discs are mounted onto hubs, the thru axle is still supposed to hold the hub (and the rest of the wheel) in exactly the right place, so if you've noticed a problem with the axle that's the most plausible cause - what do you mean by "very light"? Is the sound definitely disc rubbing, or could it be something else?

Is the headset OK? When you get out of the saddle, that could add some lateral forces on the headset...?

[sethjs]

I've had *very* few experiences on disc brake bikes where I don't produce some level of rub if I get out of the saddle. Tarmac SL7. Venge. Diverge. All of them - if I stand up and torque the bike back and forth when climbing, there's always rub. I weigh 160 pounds. I think it's almost always coming from the front - I suspect it's just the fork bending slightly.

[Steve Curtis]

It's probably the fork bending. Try centring the calliper

[Loukas]

Thanks all, you've given me some pointers to think of....

So, in order:
- Re the rotors being out of true, I tried new ones, same problem, so that was discarded
- On the possibility of the caliper is not square to the rotor face I just tried my front road wheel on the gravel bike.... the problem dissapeared, so clearly the front wheel is the issue
- Re the the thru axle being very light (30gr), this potential issue is out of the table now as I tried the road wheel with the same light axle... and no issue
- Is the headset OK?.... well, because of this possibility I thought of trying a different front wheel...., so out of the table as well
- My weight. I'm 68kg - 150 pounds, I guess that shouldn't be an issue
- Finally, is the calliper centered?, yes, when I ride on the saddle, no rubbing at all

So...., I guess the wheel is not stiff enough, is there any way to get them stiffer? more spoke tension or better/stronger spokes?

[cubixthe]

It's normal, the reason would be actually that the wheel is TOO stiff. Normally an aluminium wheel will bend at the contact point when power is put into it. A stiff wheel/rim will not bend at all making the WHOLE WHEEL move slightly at the weakest point (axle) and that results in disc rub and even rim brake rub. Think about it, for the disc brake to move actually the HUB needs to move, and that has little to do with the wheel stiffness. Might also be that the bearing preload is set on the loose side. Depending on the wheels you actually preload the bearings sometime with the thru axle, try tightening it a bit more and see if that helps a bit.

[MikeD]

Common problem. Happens on my bike too when standing out of the saddle. Try adjusting the caliper and make sure the rotor is true.

[Loukas]

Makes sense what cubixthe says about the issue being at the Hub...., but the torque spec of the Axle is 10 Nm, I've tighten that up to 12 Nm.... going higher seems risky to me.
Hub is a new DT 240, with about 1000 km...., not sure if bearings in there can be an issue in such a sort use?

[Visqu]

Center the caliper around the disc, then reset the pads. A common mistake is to center using the pads as reference.

The caliper slots are also quite narrow and you might actually be rubbing the caliper and not the pads if the caliper is not centered properly.

[TobinHatesYou]

It's probably the fork bending. Try centring the calliper

It’s almost certainly this, though centering isn’t always the answer since the fork flex is usually greater in one direction. I’ve found that the outside pad usually needs more slightly more clearance in these situations.

[Steve Curtis]

I agree. One off my bikes had always rubbed when I'm out of the saddle until I offset the calliper a bit to one side.

For the op chasing a problem it's probably best to centre them and go from there if the problem persists.

[Loukas]

Thanks. Is there any tip/tool to center the caliper?... being so precise manually is kind of an impossible mission

[billendk]

Have good luck with these from birzman.

http://www.birzman.com/products_2.php?u ... =4&Key=133


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